We seek to understand how the various optical structures in eyes, as well as the photoreceptor cells themselves, influence and limit the visual information provided to the nervous system by the axons of the retinular cells. We are concerned with processing of spectral, spatial, temporal, and polarizational information. We wish to learn the mechanisms by which these different aspects of the visual world are separated and the degree to which they are independent. We also consider mechanisms and consequences of light-adaptation and of photochemical processes. Examples of the optical components of interest are photoreceptor organelles, visual pigments and photoproducts, pigment granules, tapetal reflectors, corneal lenses, corneal interference filters, and crystalline cones. New, noninvasive techniques for making photo-chemical and physiological measurements of photoreceptor cells are being developed as part of this research. The experimental techniques employed include retinal densitometry, intracellular optical physiology, microspectrophotometry, optical microscopy, optomotor studies, electrophysiology, and analogue and digital acquisition and computation. Theoretical techniques employed include electromagnetic theory, systems theory, theoretical modeling and computer simulation. Most of this work deals with compound eyes of insects.